1. Technical Field
The present invention relates to a deodorizing method based on a polymerization reaction, an oxidization reaction, and adsorption, a deodorizer composed primarily of a metal oxide which performs a catalytic action, a method of manufacturing such a deodorizer, and a deodorizing apparatus which incorporates such a deodorizer.
2. Background Art
Conventional deodorizing methods include a masking process, an adsorption process, an ozone deodorizing process, and a catalytic process which uses a metal oxide.
The masking process vaporizes and disperses an aromatic liquid or solid for people to lose a sense of odors. The adsorption process employs an adsorbent such as activated carbon or the like to adsorb odor components. The ozone deodorizing process serves to decompose odor components with ozone. According to the catalytic process, odor components are oxidized and modified by the oxidizing capability of a metal oxide which is used.
In the masking process, since the aromatic material is eliminated in a short period of time, it has to be replaced periodically and frequently. The adsorption process needs periodic replacement of the adsorbent because the adsorption capacity thereof is limited.
The ozone deodorizing process is capable of producing a deodorizing effect for a long period of time. However, the ozone deodorizing process is expensive to carry out as it requires an apparatus for generating ozone and a catalyst for decomposing excessive ozone. The catalyst needs to be regenerated by heating or the like. Furthermore, if ozone is generated at a concentration higher than a designed level thereby deactivating the catalyst, then the ozone harmful to human beings is likely to leak out of the deodorizing apparatus. When a sulfur-based odor is to be deodorized by the ozone deodorizing process, a trace amount of toxic gas of SO.sub.3 is discharged.
The catalytic process which uses a metal oxide can maintain a deodorizing effect for a long period of time and does not produce hazardous substances. However, the catalytic process may produce other odor components. Specifically, when hydrogen sulfide (H.sub.2 S) and methyl mercaptan (CH.sub.3 SH), which are major components of a fecal odor, are brought into contact with a metal oxide such as MnO.sub.2 or CuO, the methyl mercaptan is dehydrogenated and dimerized into methyl disulfide (CH.sub.3 --S--S--CH.sub.3) which has a lower odor intensity. However, if methyl disulfide is brought into contact with a metal oxide when both hydrogen sulfide and methyl mercaptan are present, then a polymerization reaction occurs which generates methyl trisulfide (CH.sub.3 --S--S--S--CH.sub.3) and methyl tetrasulfide (CH.sub.3 --S--S--S--S--CH.sub.3). These generated substances are as malodorous as methyl mercaptan, and cannot effectively be deodorized.